Jim,

That would be part of Tim Murphy's supercharger kit.

 

The brushes which transfer power to the inside of the electric motor also wear over time .

 

To be completely accurate, the big rubber elbow on the picture I posted is from the FAST kit. Below is a picture of Murphy's version. (Not a good picture, but all I have at the moment)

I collect pictures of these engines in all states of assembly for my personal "shop manual". I got that picture from another 928 site, where a guy was announcing the birth of his "huffed" shark.

 

I thought it looked a little funny.